Question

Several of our readings in past weeks have been on the effects on health of a microbiota shift. One example is the study of malnourished Malawian twins who had developed kwashiorkor. Can Koch's postulates be extended to cover a community of microbes? Explain which of Koch's postulates were fulfilled and which were violated in this study. What experiment(s) did the scientists do to fulfill Koch's third postulate?

reference link: http://science.sciencemag.org/content/339/6119/548.full?sid=69b84ea1-59af-41bb-bd62-2ba7388ce195

Answer 1

Koch's postulates

• The Microorganism of interest must be present in all individuals suspected to be infected.
• The organism infected can be isolated from the infected individual and grown in pure culture.
• The organism from the pure culture should infect the experimental individual.
• From the experimental animal the organism should be re isolated and show that the specific organism is responsible for the disease.

Malawian twin study

• In the malawian twin study , the gut microbes of the infected individual are transfered to experimental mice directly.
• As per koch's postulate the organism must be isolated from the host and grown in pure culture before inoculating it into experimental animal.
• so, this postulate is not followed .

Experiment

• The animals are treated with ad lithium foods , similar to the diet of those Malawian twins for 1 week.
• Fecal samples from the donors are transplanted to the experimental animals through single oral gavage.
• In one of the mice the weight loss was more . The host's co-twin was healthy and the mice received the co-twins micro biota dint show greater weight loss.
• This shows the discordant phenotype depends on the kwashiorker and microbiota of gut.
• After 3 weeks the mice are treated with ready to use therapeutic foods and showed drastic weight gain.
• These results also showed that these gut microbiota of infected individual inhibits TCA cycle and there by they donot generate necessary energy which results in weight loss.